Openet Policy Control LTE(1)

© 2009 Analysys Mason Ltd. All rights reserved worldwide.

White Paper

Policy control and charging for LTE

networks

Peter Mottishaw

October 2009

Research Sponsored by Openet


networks

Table of Contents

© 2009 Analysys Mason Ltd. 2

Table of Contents

Executive summary ...................................................................................... 3

Drivers for LTE and EPC deployment .......................................................... 4

Wireless data growth drivers and forecast ........................................................... 4

The cost versus revenue challenge ..................................................................... 5

Drivers for EPC deployment ................................................................................ 7

LTE deployment timetable and phases ........................................................ 8

LTE/SAE deployment timetable ........................................................................... 8

LTE deployment phases ...................................................................................... 9

Phase 1: LTE for data only .......................................................................................... 10

Phase 2: LTE for data with hybrid voice architecture .................................................. 10

Phase 3: LTE with full IMS .......................................................................................... 11

Policy control and charging for LTE services ............................................. 13

3GPP policy and charging control (PCC) ........................................................... 13

Current charging, policy and billing implementation .......................................... 15

Phase 1: LTE for data only ................................................................................ 16

Managing the transition to full IMS ..................................................................... 17

Recommendations ..................................................................................... 19

List of Figures

Figure 1: Data Growth prediction ............................................................................................. 4

Figure 2: Cost and revenue trend for 3G networks .................................................................. 6

Figure 3: Impact of LTE deployment ........................................................................................ 6

Figure 4: Mobile network operator LTE deployment plans ...................................................... 8

Figure 5: Phase 1: LTE for data only ..................................................................................... 10

Figure 6: LTE for data with circuit switched fallback for voice ............................................... 11

Figure 7: Full LTE and IMS deployment ................................................................................ 11

Figure 8: Streaming video example ....................................................................................... 14

Figure 9: 2G/3G prepaid charging scenario ........................................................................... 15

Figure 10: Billing and charging requirements ........................................................................ 17

Figure 11: Full LTE with IMS – billing implications ................................................................. 18

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Executive summary


Executive summary

Many mobile network operators have committed to deploy long-

term evolution (LTE) technology to deal with the rapid growth in

wireless data services. LTE strictly refers only to the radio

access standards introduced by 3GPP in release 8. This is part

of a broader 3GPP program called system architecture evolution

(SAE) that includes a new all IP evolved packet core (EPC). This

White Paper explores the implications for operators on the policy

control, charging and billing systems of the deployment of

LTE/SAE. A critical component in SAE is the policy and charging

control (PCC) platform that brings together and enhances

capabilities from earlier 3GPP releases to deliver dynamic

control of policy and charging on a per subscriber and per IP

flow basis.

The most immediate driver for LTE/SAE deployment is the rapid

growth in wireless data traffic that many operators are

experiencing. LTE/SAE provides a more efficient data transport

with a much lower cost per megabyte than existing 3G

technologies. Wireless data revenue is growing much more

slowly than wireless data traffic. LTE/SAE will enable operators

to reduce the cost per megabyte and maintain data services

profitability. LTE/SAE also brings high bandwidth, low latency

and fine-grained end-to-end control over quality of service

(QoS). Policy control and charging are critical in enabling the

network operator to control and monetize these new capabilities.

Network operators will follow their LTE/SAE data deployment

with support for voice services. This will raise the question of

how to migrate the existing control layer, service layer, billing

systems and operational support systems towards a full IMS

environment. Complete replacement of these systems is out of

the question due to both costs and time scales. Network

operators will need to proceed incrementally by minimizing the

impact of LTE/SAE deployment on these adjacent systems. This

will mean focusing development effort on policy, charging and

mediation platforms that can hide the changes from the legacy

IN platforms, billing systems and operational systems.


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Drivers for LTE and EPC

deployment


Drivers for LTE and EPC deployment

Wireless data growth will be the principal driver behind the first

wave of LTE deployments. We forecast that wireless data traffic

in developed countries will increase tenfold between 2008 and

2015, and sevenfold in emerging markets over the same period.

Revenue per megabyte continues to fall, driven down by

increasing competition and flat rate pricing. Many operators will

deploy LTE to cope with data growth and deal with the

divergence of revenue and cost. However, LTE is part of a

broader SAE that will bring additional benefits. Alongside LTE in

the radio access network (RAN) operators will deploy the EPC.

Together these provide a flatter, simpler IP architecture with

lower latency and a sophisticated PCC architecture. The EPC

will also support multiple radio access networks including

CDMA, WiMAX and WLAN. This section provides more detail on

these underlying drivers for LTE/SAE deployment.

Wireless data growth drivers and forecast

Analysys Mason forecast for wireless network traffic is shown in

Figure 1.

Figure 1: Data Growth prediction

Source: Analysys Mason

The key factors behind this growth are:

Mobile operators are offering higher wireless data rates

with attractive flat rate data tariffs. This was made

possible by the deployment of 3G technologies. It is

being continued by the deployment of HSPA and other

3G enhancements.


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deployment


The use of netbooks and laptops with 3G USB dongles,

mainly by enterprise customers, will continue to grow

rapidly as tariffs become more attractive.

Device manufacturers are offering platforms with large

touch screens, high bandwidth connections and

compelling user interfaces. The Apple iPhone has been

the leader in this area, but all major device

manufacturers are now offering competing products.

Advances in mobile data services and mobile devices

have made the full Internet available to mobile end

users. This in turn has stimulated development of mobile

specific applications and services that enhance existing

Internet services such as Facebook, Google maps,

Google search, Twitter and YouTube with mobile

characteristics. These include location, operator billing,

reduced bandwidth requirements and mobile specific

user interfaces.

New types of devices and services are starting to exploit

the unique characteristics of mobile data services.

Amazon's Kindle is an example of an application specific

device that uses a dedicated mobile service. Machine to

machine type services will drive further growth in these

types of applications. Improved network coverage and

reliability will also stimulate the use of cloud computing

to simplify deployment and management of new

applications.

These factors will lead to substantial ongoing growth in wireless

network traffic per user over the next five years.

The cost versus revenue challenge

The growth in mobile data usage is good news for operators, but

comes with a big challenge; data growth will be accompanied by

a relatively modest increase in ARPU and this will result in a

significant decline in revenue per megabyte between 2008 and

2015. The cost of maintaining the existing network without LTE

will soon begin to erode operators' profit margins and will

eventually outstrip revenue, as shown in Figure 2.


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deployment


Figure 2: Cost and revenue trend for 3G networks


Compared with legacy networks, LTE improves spectral

efficiency. Furthermore, LTE employs a flat-RAN architecture,

which also reduces the number of network nodes. Jointly, the

benefits of improved spectral efficiency and flat-RAN

architecture reduce network carriage costs and create a cost-

growth curve that tends to track revenue rather than demand,

allowing the operator to maintain a healthy profit margin, as

shown in Figure 3.

Figure 3: Impact of LTE deployment


Compared with previous access technologies, like GSM, CDMA

or UMTS, the smaller size of the LTE access node brings other

operational gains, including easier and quicker sitting of the


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deployment


node, lower power consumption and a much smaller space

requirement.

Drivers for EPC deployment

In addition to the cost advantages provided by the combined

LTE/EPC deployment, there are a number of other drivers for

EPC deployment.

EPC is designed to support non-3GPP radio access

networks including WiMAX, CDMA and WLAN and

3GPP 2G/3G radio access networks. It includes mobility

between these technologies and the concept of trusted

and non-trusted radio access networks.

EPC provides a simplified all IP architecture when

combined with LTE and delivers a low cost and low

latency infrastructure.

EPC includes a sophisticated PCC architecture that

enables dynamic control of IP services on a per-

subscriber and per-IP flow basis. This includes support

for fine-grained QoS and enables application servers to

dynamically control the QoS and charging requirements

of the services they deliver. It also provides improved

support for roaming. Dynamic control over QoS and

charging will help operators monetize their LTE

investment by providing customers with a variety of QoS

and charging options when choosing a service.

Examples would be bandwidth tiered services or

purchasing limited time access to specific content or

enhanced QoS.

In combination with IMS, EPC provides a future proof

path to the replacement of all legacy circuit switched

infrastructure within an all IP control layer. However, it

will be many years before we see the end of the circuit

switched infrastructure.


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LTE deployment timetable

and phases


LTE deployment timetable and phases

In this section we focus on the timetable for deployment of

LTE/SAE devices, networks and services and the factors each

mobile operator well need to consider in making deployment

decisions. We also look at the scenarios for LTE and EPC

deployment and consider how the existing control layer for voice

and messaging services will migrate towards an IMS control

layer.

LTE/SAE deployment timetable

Technology, devices, spectrum and demand, along with the

operator’s business strategy, are the main factors that will

determine the timing and strategy for LTE/SAE deployment for

any particular operator. These will be different for each operator.

Operators will need to consider their local choices carefully, in

order to achieve an optimal position to deal with future data

demand and demands on their revenue. The announced

deployment timetable for a number of operators is shown in

Figure 4.

Figure 4: Mobile network operator LTE deployment plans

Source: Analysys Mason and operator announcements

A critical determining factor in the rollout of LTE-based services

will be the availability of LTE capable devices. LTE devices will

be introduced in phases:

LTE USB modems or data cards are just becoming

available and will achieve volume shipments in 2010.

AT&T

Trials: now

Launch 2012


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and phases


These will support the initial focus for LTE on data-

intensive services for laptop and netbook users.

LTE Handsets will first become available in 2010 but will

not ship in volume until 2011 or 2012. Voice handsets

will require 2G/3G radios to support fallback to circuit

switched voice unless the network supports VoIP over

LTE.

Laptops with embedded modules will be available in

2011.

Within two or three years, the dominant device for mobile

broadband access will be the laptop with an embedded module.

In the longer term, the delivery of LTE services will not be limited

to traditional devices, but will instead extend to a range of

devices including cameras, cars, energy monitors,

environmental sensors, health-monitoring devices and many

other devices.

LTE deployment phases

There are many technology choices that operators will face

when deploying LTE. These include decisions about services,

spectrum, network and devices. The focus for this White Paper

is on the charging and policy control aspects of LTE/SAE. These

are intimately connected with the deployment of the EPC and in

the longer term the migration to an all IP control layer based on

IMS standards. This will enable a rich set of voice, messaging

and other session based services that will eventually replace

existing voice and messaging services. However, IMS is not

required for the delivery of LTE's data capabilities and so

operators have the option of incrementally moving towards the

long-term vision of an all IP LTE/EPC/IMS environment.

We identify three phases that operators will consider;

Phase 1: LTE for data only

Phase 2: LTE for data with hybrid voice architecture

Phase 3: All IP LTE/IMS environment for voice and data

We address these in more detail in the following paragraphs.

Each represents trade-offs between the end user experience

and the cost of upgrading or replacing infrastructure and

software systems. Phase 1 will support the needs of wireless

broadband for enterprise laptop users. Phase 2 addresses the

needs of LTE handsets to support voice using some of the

existing voice infrastructure. This minimizes additional

investment but constrains the service that can be offered. Phase

3 provides the full potential of an all IP rich communications


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and phases


experience, but with major investment in new infrastructure and

systems.


Initial deployments of LTE will be to provide data services for

enterprise customers using LTE USB modems with laptops. LTE

will be provided first in areas of heavy data traffic and USB

modems will support fallback to 3G data services where LTE is

not deployed. LTE provides a compelling service with the

benefits of higher bandwidth, end to end QoS, and low latency.

LTE deployments to support these types of services will

effectively be independent overlays (see Figure 5) to existing

networks sharing physical locations and some IP infrastructure.

They will include PCC functionality to support data services and

will be integrated into existing pre-paid and post-paid billing

systems. The full implications of this phase are explored in the

following chapter.

Figure 5: Phase 1: LTE for data only


Phase 2: LTE for data with hybrid voice architecture

Some difficult questions will need to be faced when LTE

handsets become available and operators need to provide voice

and messaging services. Operators have massive investments

in the circuit switched infrastructure. This includes the IN/SS7

control layer, IN pre-paid platforms, IN value-added services

platforms, mediation platforms, billing systems and operational

support systems.

A number of approaches have been developed that enable

operators to reuse these existing platforms when offering voice

services to LTE handsets. The simplest is to fallback to existing

2G/3G circuit switched connectivity for voice and messaging

services. In this phase the mobile device will be required to


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and phases


support both LTE and 2G/3G radios. Indications are that to

preserve battery life the device will switch of other radios when

the LTE radio is in use. Voice and messaging services will

require use of the 2G/3G radio where as data services will be

provided by the LTE radio. (See Figure 6)

Figure 6: LTE for data with circuit switched fallback for

voice


This approach satisfies the need to keep existing infrastructure

but limits the use of voice and data together and will not allow

the rich communications services that IMS can offer. There are

various approaches being standardized that provide an

incremental step in this direction without the wholesale

replacement of the circuit switched systems. These include the

VoLGA and VoLTE approaches. These can deliver voice over IP

and will start to make use of some of the dynamic policy control

capabilities of the EPC.

Figure 7: Full LTE and IMS deployment


Phase 3: LTE with full IMS

A move to an all IP LTE/IMS environment (see Figure 7) brings

the advantage of integrated access to all voice, messaging and


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and phases


data services over a single LTE access. It also provides the rich

communications services that IMS was originally created for.

However, the move to all IP will require the replacement of the

legacy circuit switched control layer and the replacement of a

number of its operational systems. Major system integration

projects will be required to adapt the systems that are not

replaced to the requirements of an all IP environment. Most

operators will choose and incremental approach to addressing

these challenges.


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Policy control and charging

for LTE services



services

In this section we will focus on the impact of LTE on policy

control, charging and billing mediation requirements. Most of the

discussion is focused on phase 1, but operators must consider

the long term plan to move to full IMS.

3GPP policy and charging control (PCC)

The PCC capabilities in 3GPP release 8 build on earlier releases

to provide a rich policy and charging environment supporting

dynamic control of QoS, charging and policy by application

servers. To illustrate the capabilities of the 3GPP PCC

architecture we will use the example of a video streaming

session delivered across the EPC and LTE (see Figure 8). To

make it more interesting we include a two sided business model

where the video stream can be delivered by a third-party paid for

by advertising. This type of scenario will become increasingly

common as LTE is rolled out.

The PCC functions include:

PCRF (policy and charging rules function) provides

policy control and flow based charging control decisions.

PCEF (policy and charging enforcement function)

implemented in the serving gateway, this enforces

gating and QoS for individual IP flows on the behalf of

the PCRF. It also provides usage measurement to

support charging

OCS (online charging system) provides credit

management and grants credit to the PCEF based on

time, traffic volume or chargeable events.

OFCS (off-line charging system) receives events from

the PCEF and generates charging data records (CDRs)

for the billing system.

In the example shown in Figure 8 a customer has requested a

streaming video that will be paid for by the included advertising.

We will assume the customer likes the video and decides after

five minutes to pay for a higher data rate with no advertising

from her pre-paid video account. This requires specific QoS

treatment to the requested and modified by the streaming video

controller during the session. It does this by appearing as an

application function to the PCRF. The PCRF and PCEF work

together to ensure the correct QoS is provided. The charging

aspects are managed by the OCS. When the customer switches


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for LTE services


to the non-advertising stream the PCEF will request credit from

the OCS. The OCS will check the customer’s video balance and

provide the appropriate credit for the IP flow. The OCS has the

job of correlating charging events to ensure the customer is not

charged for the data stream, but only the video.

Figure 8: Streaming video example


This scenario could be implemented in many ways and the

complexity of subscriber management, off-line charging and the

possibility of the video service being provided by a third party is

not included here. But the key message is that the PCC

capabilities brought together in 3GPP release 7 and enhanced

with release 8 are sufficiently powerful to provide dynamic

control of charging and QoS on a per flow and per subscriber

basis.

This example also illustrates the sorts of demands that will be

put upon the PCC as LTE is deployed. The main sources of

growth in transaction growth will be;

The support for dynamic control of policy and charging

will enable applications to make multiple requests per

service session.

Triggers associated with changes in location, network

access, device status and security will generate

additional requests.

The greater complexity of the new business models

illustrated in the example will also push the transaction

rates higher.


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for LTE services


As a result the overall transaction load on the PCC will increase

significantly from current levels.

Current charging, policy and billing

implementation

Figure 9: 2G/3G prepaid charging scenario


In current 2G/3G networks policy control, charging and billing

mediation are already complex functions. Real-time charging is

provided using the following platforms (see Figure 9):

IN pre-paid platform: originally deployed to provide

simple pre-paid voice services, has been continuously

extended to include roaming, messaging, data and

content services to pre-paid customers.

Active mediation platforms: have been deployed as

adjunct platforms to the IN pre-paid platform to support

control and usage measurement for messaging, data

and contents services.

Complex real-time rating platforms: have been deployed

as adjunct platforms to the IN pre-paid platform to

support more complex tariff models and subscriber

models.

Policy control is already implemented to support existing

data services. This includes some PCRF type

functionality, but not the full dynamic control of policy

that the EPC will provide.

GGSN and dedicated deep packet inspection (DPI)

platforms support active mediation by enabling very

detailed usage measurements and control of IP flows.

The growth in data rates and the roll out of LTE will put


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for LTE services


an increasing load on these functions as they migrate to

the PDN GW in the EPC.

Billing mediation integrates with existing 2G /3G network

elements to support the post-paid billing requirements.

This real-time infrastructure is being integrated with offline billing

to support a hybrid model; where a customer can choose to

have individual services billed on a pre-paid or post-paid basis.

The fundamental issue operators will face is how this already

complex policy control, charging and billing infrastructure will

evolve to accommodate the needs of LTE. A migration path is

required from the legacy environment of Figure 9 to the

LTE/SAE architecture of Figure 8. The growth in transaction

rates that the PCC will be required to support will drive the

replacement of most legacy components during the migration.

The IN pre-paid platform in particular will be gradually eliminated

as balance management migrates to the online billing platform

and the circuit switched infrastructure is eventually replaced.


The evolution of policy control, charging and billing to support

phase 1 is illustrated in Figure 10. The critical implications are;

Active mediation systems and complex real-time rating

adjuncts must evolve to support the requirements of the

3GPP to find OCS. Rapidly growing usage will put a

significant load on the systems and they will need to be

scaled accordingly.

The migration of functionality away from legacy IN pre-

paid platforms will continue. Operators are already

moving in this direction to support more complex

hierarchical accounts and enable subscribers to choose

how individual services are charged (pre-paid or post-

paid).

The PCRF capability should be the focus for any

enhancements to policy control. Implementation on the

PCRF enables policy control to be used for both pre-

paid, post-paid and hybrid billing.

Existing billing mediation platforms will need to be

extended to support the EPC elements. With rapidly

increased data traffic these will need significant scaling

to meet demand.

Existing off-line post-paid billing systems are complex

and expensive to upgrade. Where possible operators

should insulate billing systems from the changes in the

network by focusing on enhancements to the PCC.


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for LTE services


The streaming video example at the start of this section

illustrated the type of premium service that LTE can

offer. This is critical to supporting additional revenue

streams and the PCC functionality must be evolved to

support this type of scenario.

Figure 10: Billing and charging requirements


Managing the transition to full IMS

Phase 1 will be the focus for most operators for at least the next

three years. However, it is important to remember the longer

term evolution to phase 2 and eventually phase 3, when

planning upgrades to the policy control, charging and billing

systems.

Phase 2 deliberately minimizes the changes to the existing

circuit switched infrastructure including policy control, charging

and billing systems. However, the variance on phase 2 that

include VoIP delivered over LTE will require the full dynamic

QoS controls standardized in the EPC. These are required to

ensure appropriate QoS for voice calls and use a similar

mechanism to the video streaming example in Figure 8.

Phase 3 is the transition to an all IP network for transport,

signaling and control based on IMS, EPC and LTE standards. A

typical deployment is illustrated in Figure 11. There is likely to be

a proliferation of application and content servers that will use the

application function to manage quality of service and charging

requirements. This will generate a much higher load on the

policy and charging control platform. Operators should factor in

the scalability requirements of these future needs when

selecting solutions to the current data only scenario.


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for LTE services


Figure 11: Full LTE with IMS – billing implications


In Figure 11 the IN pre-paid platform has finally been retired

from service and the real-time charging functions migrated to the

PCC and online billing systems. Operators should have this

transition in mind when planning for the implementation of a data

only LTE.


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Recommendations


Recommendations

Mobile network operators are faced with some difficult decisions

in deciding how to evolve their charging, policy management

and billing mediation platforms as they deploy LTE and EPC.

The critical trade-off is between delivering the full potential for

LTE and IMS to enrich the end user experience and the cost of

replacing and upgrading the existing control plane and support

systems. The end user experience, with the appropriate

charging and billing infrastructure, can be translated into

increased revenue and customer loyalty. The release 8 PCC

capabilities will be an enabler for new differentiated services and

new business models. Moving beyond a simple flat rate to

offering customers the choice of bandwidth, QoS, advertising

funded services and the like will be important in monetizing the

LTE investment. The final choice of how to balance revenue and

cost will depend on a particular operator’s situation, but the

following issues should be considered with relation to charging,

policy control and billing systems;

LTE/SAE supported data services can deliver significant

new value to the end customer with increased

bandwidth, reduced latency and fine-grained control

over QoS. The value can only be realized by flexible

charging, policy management and billing solutions. The

ability to rapidly deploy new charging models and

integrate QoS policies will be critical to competing and

succeeding with LTE. Operators must include these

requirements in their LTE/SAE rollout plan.

Billing systems have proved to be costly and time-

consuming to upgrade. Operators can minimize the

impact of this by using the mediation and charging

platforms to hide major changes from the billing system.

These tend to be more modern platforms and therefore

less costly to upgrade. It is also easier to share

capabilities between pre-paid and post-paid billing

systems and support evolution towards converged

billing.

Online charging will continue its complex evolution from

IN platform to full IMS online charging system.

Introduction of an LTE/SAE data service will increase

this complexity; requiring management of QoS and

requiring greater scalability. Most operators recognize

that IN platforms will be around for some time. The

focus should be on opening up standardized interfaces


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Recommendations


to the IN platform so that new requirements can be

deployed on adjunct platforms. This will help with the

migration of functions (subscriber management, real-

time rating, tariff models, etc) from the IN platform to the

online billing platform that will be the core platform when

and all IP LTE/IMS implementation is achieved.

Providing voice over LTE with IMS support for rich

communication services can add significant value to the

services offered. In evaluating intermediate steps to

supporting full IMS operators should carefully evaluate

how any upgraded or new systems will support the final

IMS architecture.

Deployment of full IMS capabilities will significantly

increase the volume of charging and policy events that

the policy and charging control and mediation functions

must deal with. The likely proliferation of application

servers supported by IMS will amplify this trend. As a

consequence operators must evaluate carefully the

scalability and performance of systems deployed during

the transition phase to full LTE/IMS deployment.

Deployment of more powerful DPI capabilities, either

standalone or as part of the PDN gateway will be

important in supporting some of the more sophisticated

new service opportunities. Operators should evaluate

the requirements and scalability of these platforms as

part of their overall PCC deployment.

Policy and online charging will become increasingly

connected as the network evolves towards full LTE/IMS.

As a consequence operators must evaluate how these

will integrate over time.

Documents

Openet Policy Control LTE(1)